[flags] Delete enableDebugTracing (#31780)

This is unused, even in the one builds that uses it, and we don't plan
on landing it in this form.

Author: rickhanlonii

packages/react-dom/src/__tests__/ReactDOMServerIntegrationModes-test.js

@@ -37,56 +37,6 @@ describe('ReactDOMServerIntegration', () => {
     resetModules();
   });
 
-  // Test pragmas don't support itRenders abstraction
-  if (
-    __EXPERIMENTAL__ &&
-    require('shared/ReactFeatureFlags').enableDebugTracing
-  ) {
-    describe('React.unstable_DebugTracingMode', () => {
-      beforeEach(() => {
-        spyOnDevAndProd(console, 'log');
-      });
-
-      itRenders('with one child', async render => {
-        const e = await render(
-          <React.unstable_DebugTracingMode>
-            <div>text1</div>
-          </React.unstable_DebugTracingMode>,
-        );
-        const parent = e.parentNode;
-        expect(parent.childNodes[0].tagName).toBe('DIV');
-      });
-
-      itRenders('mode with several children', async render => {
-        const Header = props => {
-          return <p>header</p>;
-        };
-        const Footer = props => {
-          return (
-            <React.unstable_DebugTracingMode>
-              <h2>footer</h2>
-              <h3>about</h3>
-            </React.unstable_DebugTracingMode>
-          );
-        };
-        const e = await render(
-          <React.unstable_DebugTracingMode>
-            <div>text1</div>
-            <span>text2</span>
-            <Header />
-            <Footer />
-          </React.unstable_DebugTracingMode>,
-        );
-        const parent = e.parentNode;
-        expect(parent.childNodes[0].tagName).toBe('DIV');
-        expect(parent.childNodes[1].tagName).toBe('SPAN');
-        expect(parent.childNodes[2].tagName).toBe('P');
-        expect(parent.childNodes[3].tagName).toBe('H2');
-        expect(parent.childNodes[4].tagName).toBe('H3');
-      });
-    });
-  }
-
   describe('React.StrictMode', () => {
     itRenders('a strict mode with one child', async render => {
       const e = await render(

packages/react-reconciler/src/DebugTracing.js

@@ -32,7 +32,6 @@ import {
   enableScopeAPI,
   enableLegacyHidden,
   enableTransitionTracing,
-  enableDebugTracing,
   enableDO_NOT_USE_disableStrictPassiveEffect,
   enableRenderableContext,
   disableLegacyMode,
@@ -80,7 +79,6 @@ import {NoLanes} from './ReactFiberLane';
 import {
   NoMode,
   ConcurrentMode,
-  DebugTracingMode,
   ProfileMode,
   StrictLegacyMode,
   StrictEffectsMode,
@@ -89,7 +87,6 @@ import {
 import {
   REACT_FORWARD_REF_TYPE,
   REACT_FRAGMENT_TYPE,
-  REACT_DEBUG_TRACING_MODE_TYPE,
   REACT_STRICT_MODE_TYPE,
   REACT_PROFILER_TYPE,
   REACT_PROVIDER_TYPE,
@@ -630,13 +627,6 @@ export function createFiberFromTypeAndProps(
           return createFiberFromTracingMarker(pendingProps, mode, lanes, key);
         }
       // Fall through
-      case REACT_DEBUG_TRACING_MODE_TYPE:
-        if (enableDebugTracing) {
-          fiberTag = Mode;
-          mode |= DebugTracingMode;
-          break;
-        }
-      // Fall through
       default: {
         if (typeof type === 'object' && type !== null) {
           switch (type.$$typeof) {